With most recent gift, about 43% of his 2006 holdings have been given to foundations

Berkshire Hathaway Inc.
BRK.B -0.71%
Chairman Warren Buffett has donated shares valued at $3.4 billion to five foundations, marking another round in his pledge to donate most of his wealth to charities and philanthropic endeavors.

On Monday, the company said Mr. Buffett, 87, had converted 11,867 shares of his Berkshire Hathaway Class A stock into roughly 17.8 million shares of Class B stock. He then donated roughly 17.7 million Class B shares to the Bill & Melinda Gates Foundation, Susan Thompson Buffett Foundation, Sherwood Foundation, Howard G. Buffett Foundation and the NoVo Foundation.

In 2006, Mr. Buffett pledged to donate 85% of his stake in Berkshire Hathaway to the foundations, with most going to the Gates Foundation. He made a similar contribution last year, with that round of stock valued at about $3.17 billion. With this most recent gift, about 43% of his 2006 holdings have been given to foundations, with a total value of about $31 billion based on the value at the time of the gifts, the company said.

Mr. Buffett owns 37.8% of the Class A shares outstanding in Berkshire Hathaway, according to FactSet.

Mr. Buffett intends to have all of his Berkshire shares given to philanthropy through annual gifts, expected to be completed 10 years after his estate is settled, the company said.